It is the season of lights and tinsel, choirs and carols, the aroma of pine and roasting chestnuts. Christmas comes to us with sumptuous meals, hearty laughter, and kisses beneath the mistletoe. Christmas scenes — by the old masters and by modern advertisers — decorate the walls of museums, billboards on the roadside, and cards in the mailbox. For nearly 2,000 years, the world has marked the birth of Jesus Christ as its most festive jubilee. No other day of the year offers the world so many earthly pleasures.

But why? No pope or Church council ever declared that it should be so. Yet every year, Christmas comes onto the calendar like a sudden December wind, like the blinding sun reflected off new snow. It is a shock to the senses, to go from barren winter to the season of lights and feasting.

And so it should be, for the first Christmas — the day when Jesus Christ was born — was a shock to human history.

For millennia, humankind had lived and died, uncomprehending, in its sin, the miseries of this world inevitable and the joys few and fleeting. Then Christmas arrived, and even the calendar went mad. From that moment, all of history was cleft in two: before that day (B.C.), and after that day (A.D.). The world — with all its sights and sounds and aromas and embraces — was instantly transfigured. For the world’s redemption had begun the moment God took human flesh for His own, the moment God was born in a poor stable in Bethlehem.

The greatest Christian poem commemorates this moment when God definitively came to dwell on earth. St. John begins his Gospel by describing a God of awesome power, remote in space and transcending time: a Spirit, a Word:

In the beginning was the Word, and the Word was with God, and the Word was God. He was in the beginning with God; all things were made through Him.

This is the God that even the pagan philosophers knew: the Prime Mover, the One, the Creator. Yet, precisely where the pagan philosophers stalled, John’s drama proceeded to a remarkable climax:

And the Word was made flesh, and dwelt among us.

This was shocking news. From the distant heavens, from remotest time, God Himself had come in flesh to “pitch His tent” among His people. Yes, God is eternally the Word, but a word is elusive, and not everyone may grasp it. Now He is also a baby, and a baby may be picked up and held and embraced.

Of all the amazing and confounding truths of the Christian religion, there is none so outrageous as this: that the Word was made flesh, in a particular little town, in a stable filled with animals, on a certain day of the year. The Word was made flesh and changed everything. This makes Christmas the most shocking feast in the calendar.

And all the meaning of Christmas is summed up in this fact. God lived in a family the way we do. He shivered against the cold the way we do. The Word-made-flesh nursed at His mother’s breast like any other human baby. Suddenly, God was not a watchmaker, some remote mechanic who wound up the world and let it go. God was a baby, crying to be picked up.

Tradition tells us that John wrote the Prologue to his Gospel in a white heat of inspiration. His friends had asked him to set down the story of Jesus, so he asked them a favor in return: to fast and pray with him. When the fast was over, the Spirit came upon John, and he could not contain himself. The words poured out — perhaps the very words he had been trying to say all his long life, but had never quite managed to find before.

You can hear the astonishment in his voice when he tells us that the Word was made flesh. As he was writing, he must have felt that same thrill again, the thrill he felt when it first hit home that this Jesus, the carpenter from Nazareth, was the Anointed, the Son of God.

And that same astonishment carries over into his first epistle. According to tradition, John wrote that letter sixty-six years after the Ascension of Christ, but the amazement is still fresh in his voice. He still can hardly believe that “that which was from the beginning” is also that “which we have heard, which we have seen with our eyes, which we have looked upon, and our hands have handled.”

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In the earliest days of the Church, Christmas was not one of the important feasts. Jesus’ life was still a living memory, and His extraordinary resurrection rightly occupied the central spot in the calendar. But as time went on, false teachers began to deny the fact of Jesus’ humanity. They claimed that Jesus’ body had been an elaborate disguise, that, in reality, God had never debased Himself by taking on human flesh. Later heretics denied also that Mary gave birth to the Word: instead, they said, she gave birth to a “vessel” into which the Word was later poured. Still other heretics believed that the Son was a subordinate being — divine, but not coeternal with God the Father.

All these heresies had one thing in common: an unwillingness to face the apparent foolishness of the Incarnation. Arius, the founder of the Arian heresy, was an eminently reasonable man. He denied the doctrine of the Trinity because, he said, three cannot be one; that’s elementary arithmetic. The infinite God cannot become finite man; that’s elementary philosophy. Therefore there could be no Incarnation.

Heretics like Arius wanted to spare God the unreasonable indignity of being corrupted by too close an association with humanity. It was the same problem the Pharisees could not get over: If this Jesus is so good, why does He associate with sinners and tax collectors? In fact, though the heretics would have insisted that they were defending the perfection of the Deity, they were actually denying the perfection of God’s love. Love, after all, can seem unreasonable. Anyone who values another as much as oneself seems entirely unreasonable.

It can hardly be coincidence that the celebration of the literal, historical birth of Jesus the carpenter’s son began to take on more importance just when the true faith was most dangerously beset by these flesh-denying errors. The scandalously human birth of the Son of God was the very thing that separated orthodoxy from heresy. Celebrating that Nativity committed the Church to a clear statement of principle.

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In the beginning, there was no universal agreement on the date of Christmas. The Church in Egypt at first placed the date of Christ’s birth in May or April. Others put it in March, and still others in any other month you care to name. It was also popular to combine the celebration of Christ’s birth with the celebration of the Epiphany, putting them both on January 6. But sometime in the 400s the date of the Feast of the Incarnation settled on December 25, and there it stayed.

There are at least three plausible theories to account for how Christmas came to be celebrated on December 25. No one of the theories excludes the others; all three could be correct.

The first theory is the simplest. An old story says that, in about the year 350, Pope Julius I looked up the date of Jesus’ birth in the census records. Certainly there is nothing outlandish in the idea of census records holding that information even three and a half centuries later. We know from Luke’s Gospel that Jesus was born during a census. The Romans, with their almost compulsive love of order, might well have kept those records forever in some bureaucratic hole in Rome.

The second theory has it that Christians, unable to stamp out a pagan midwinter celebration, simply took it over. Throughout history, people have celebrated the passing of the shortest day in the year, the solstice. When the days begin to lengthen again, it means that the death of winter will certainly pass, and the world will be reborn in spring.

The pagan origin of the date should not scandalize us. Indeed, many Christmas traditions have pagan origins. The Christmas tree, for example, has no obvious connection with the birth of Jesus, but certainly makes sense as a pagan midwinter rite: By sympathetic magic, we bring back the dormant spirit of vegetation when we bring an evergreen tree — still living when everything around it is dead — back from the forest. And yet it is an appropriate symbol for Christians, too. The evergreen tree is an obvious metaphor for the hope of new life that Christ brought us.

Again, the lights we string everywhere for Christmas may be a survival of an old heathen rite — once again, a kind of sympathetic magic, lighting fires to bring the dying sun back to life. But light has always been a favorite Christian symbol, too.

We know that the early Church frequently took advantage of local beliefs or customs to spread the Gospel. Paul himself founded one of his most famous orations on the altar to an unknown god in Athens. “What therefore you worship, without knowing it,” he told the gawking Athenians, “that I preach to you.” (Acts 17:23.) It would be very much in the spirit of Paul for the Church to develop a Christian interpretation of a beloved heathen festival, explaining to eager converts that they were really worshipping not the light, but the Light.

The third theory to account for the specific date December 25 is that it corresponded with the early Church’s notion of Jesus’ perfect life. Tradition had it that Jesus died on March 25. In order for His life to be appealingly perfect, the theologians reasoned, He must also have been conceived on March 25, then born exactly nine months later.

The idea of Jesus’ life having a kind of aesthetic perfection must have been satisfying to an age still under the spell of Neoplatonist philosophy. It would have satisfied the intellect, and that Roman passion for order, as much as the continuation of the beloved midwinter festival satisfied the sentiments.

All of these theories could be true. One can imagine, for example, the Pope discovering the date in census records, and the Church taking advantage of its happy correspondence with the date of a favorite pagan festival, even as the more philosophical Christians capitalized on its appealing symmetry with the traditional date of Jesus’ death. As always, Christians would have reached out to the nations in ways the nations were prepared to hear. By giving a Christian interpretation to a favorite local custom or an appealing philosophical idea, the Church gave the newly converted a way of seeing the story of the Incarnation in terms they could understand.

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As the festival spread throughout the newly Christianized nations of Europe and the East, it gathered more old pagan customs and gave them new Christian interpretations. Everywhere Christmas went, it must have seemed new but somehow familiar to newly converted pagans. Perhaps that very familiarity made it the most beloved feast in the calendar.

At any rate, by about 1100, Christmas had become the most important celebration of the year. Throughout the high Middle Ages, Christmas was celebrated everywhere with tremendous spectacles and rejoicing. The people sang their favorite carols; psychedelic processions wound noisily through the narrow streets of medieval cities; and everywhere there was the heavenly aroma of Christmas cooking.

With the Protestant Reformation, however, came changes on the cultural scene. In their zealous rage against any perceived abuses in the Church, many of the Reformers targeted Christmas as nothing more than a mishmash of heathen festivals. In a sense, of course, they were correct: many of the traditions did come from pagan roots. But the anti-Christmas factions judged by the stem when they ought to have judged by the fruit.

When the Puritans took over in England, they banned Christmas outright. Shops were ordered to stay open. Anyone caught with a mince pie was in serious trouble. All the greenery, Yule logs, plum puddings, and carols that make up a traditional English Christmas were (the Puritans said) nothing but heathen idolatry, and heathen idolatry must be suppressed. There were stubborn pockets of resistance — some people were even willing to die for Christmas, so strong was the popular attachment to the traditional holiday — but the Puritans prevailed, though only for a while.

To counteract all that heathen wallowing in sensory pleasures, the Puritans decreed that Christmas would be a day of fasting. Somehow that tradition never caught on. It would be easy to say that the fast never caught on because of human weakness — people, after all, prefer feasting to fasting almost as naturally as they prefer joy to sorrow. But Lent never dropped out of the calendar from lack of demand. Good Christians are willing to endure self-denial when it seems appropriate. It just does not seem appropriate for Christmas.

What the Puritans could not understand, and what many good people still fail to understand, is that there is no contradiction between worshipping God and enjoying God’s creation. It is no shame to enjoy the good things God has given us. Jesus’ first recorded miracle was turning water into wine — and not just ordinary wine, St. John is careful to point out that this was the good stuff. Apparently, the Son of Man had, in the most human and fleshly sense, good taste.

Some misguided Christians, like the Puritans, are ashamed to sully the affairs of faith with earthly enjoyment. But the miracle of Christ’s birth is that it was earthly. The Word became flesh — real, unmistakably earthly flesh. “Flesh,” said St. Athanasius, the heroic champion of orthodoxy when the clouds of heresy seemed blackest, “did not diminish the glory of the Word; far be the thought. On the contrary, it was glorified by Him.”

Some Church Fathers called Christmas the Feast of the Incarnation.

Incarnation comes from a Latin word that means “enfleshment.” What sounds to English-speakers like a rarefied theological term is really just a statement of fact: God took on flesh. When that happened, flesh itself became something holy, something to be celebrated with paintings and statues and Christmas cards.

Yet in the eighth century, a faction arose in the Church calling themselves “Iconoclasts,” Greek for “picture-smashers.” The iconoclasts tried to “purify” and “spiritualize” Christian life by obliterating all artistic representations of Jesus, Mary, and the saints. They seized and destroyed most of the religious images in the Eastern Roman Empire, and they cut off the hands of those Christians who would not part with their icons. God, they said, could not be represented in a picture; any attempt to do so was rank idolatry. But this is how St. John of Damascus answered them: “In former times, God, being without form or body, could in no way be represented. But today, since God has appeared in the flesh and lived among men, I can represent what is visible in God. I do not worship matter, but worship the creator of matter Who became matter for my sake . . . and Who, through matter, accomplished my salvation.”

In other words, the Incarnation makes art, too, a holy thing, just as it made the body a holy thing. The artists who have painted the Nativity throughout the centuries were not creating idols. Their visible representations are hymns of praise to the invisible God made visible.

Look at any of the classic Nativity paintings and marvel at the care taken with the tiniest details. Every animal in the stable is an individual creature; every straw in the manger seems to be drawn with infinite care. Of all the biblical scenes artists have loved to paint for centuries, the Nativity is the one that seems to provoke the most thorough delight in the simple pleasure of drawing things. It seems as if God is in every detail.

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Everyone’s favorite Christmas story is the one in Luke’s Gospel. What makes it so beloved is the familiarity of it all. Luke, who seems to have been writing for a gentile audience, strives to place Jesus exactly in history and geography. His point is that the birth of the Christ is not a metaphor or parable (something a sophisticated Mediterranean audience, accustomed to hearing the philosophers and sophists reinterpret classical mythology allegorically, would easily be tempted to suppose). It was a real event in a real place, related in a precisely knowable way to the other real events of recent history.

Having established the exact time and place, Luke goes on to give us, with a professional historian’s skill, exactly the details we need to bring home the earthly reality of Jesus’ birth. We learn how Joseph and Mary felt when they found there was no room at the inn, and how grateful they were for even the scant shelter of a stable — not because Luke tells us how they felt, but because he gives us just enough detail to put us right there with them, and we can feel it for ourselves. Probably no one could ever make a movie out of those events that would really convince us: We were there, we know what it was like, and whatever we saw on the screen or on the stage would never seem half so real.

The other Gospel writers do not provide the same details. They have their own points to make, each one as valuable as Luke’s — but not so immediately appealing to our sentimental side.

Mark is the only one who has nothing to say about Jesus’ birth. His compact and economical narrative begins with John the Baptist and wastes no time getting Jesus baptized by him.

Matthew tells us only that Jesus was born in Bethlehem, then skips straight to the Wise Men. Matthew and Luke seem to have been writing for different audiences: Matthew for people who had heard of or seen Jesus the man and needed to know that He was also Jesus the Christ, and Luke for people who had heard of Jesus the Christ and needed to be told that He was also Jesus the man.

And then there is John. He actually tells the same story as Luke, but in words so different that at first we do not recognize the story at all. We could almost say that, where Luke saw the events from earth’s point of view, John saw them from heaven’s. Luke gives us the details that let us see the earthliness of the Incarnation; John gives us the poetry that lets us see the miracle of it all.

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It is important to have John’s divine words in mind when we read the story in Luke, because the Incarnation was not a one-time event that ended on the Cross or with the Ascension. Jesus Christ came into the world in a particular place at a particular time, but He established a Church that would be His body in the world. The gloriously diverse congregation of believers who inhabit every corner of our planet — they are Christ’s body. If you want to know what Jesus looks like, go to church and look around you.

Even more, we encounter the Lord in the flesh in the Holy Eucharist. “For My flesh is real food,” He said, “and My blood real drink.” The Incarnation is not an abstract principle — it is a miraculous concrete fact every day of our lives. It didn’t just happen two thousand years ago. It happened today.

The “incarnational principle” — that embodiment of love — is present in all the sacramental realities Jesus gave us. It is not simply for the sake of weak human understandings that all the sacraments are celebrated with physical signs. God the Son made the physical sacred.

In the Holy Eucharist itself, we see the nourishment for our spirits expressed in the most elementary form of nourishment for the body. The eternal God appears to us in the very temporal form of bread and wine. “This is My body, broken for you,” Our Lord told us. “This is My blood, shed for you.” As often as we celebrate the Eucharist, we are roused to remember that Jesus the Son of God had real flesh to break and real blood to shed.

That fact is what the Feast of the Incarnation celebrates, and it is what makes enjoying the pleasures of the senses feel so appropriate for Christmas. Throughout His earthly ministry, Jesus of Nazareth healed the sick and fed the hungry. He loved us not just enough to take us with Him into paradise, but to wish us every happiness while we still live here on Earth. And the only thing He asked us to do in return was to love Him, and to love others as much as He loved us.

You can still see traces of that Christian love in the ancient and beautiful custom of giving Christmas presents. There is more than a little irony in the fact that today’s manic rush to buy and sell Christmas exists only because we have managed to pervert the beautiful Christian urge to give. That perversion is the very sin that Jesus Himself condemned most angrily when He drove the moneychangers out of the Temple, the only sin that could have driven Him to use a whip on the sinners. What does Jesus think when he sees our “Sparkle Season,” the modern midwinter festival of greed? Perhaps (for Jesus is more perfectly forgiving than we could ever be) He sees the good in us, and the earnest desire many of us have to make others happy, and forgives us our excesses. We should pray that it might be so.

But we should not be ashamed to enjoy the beautiful traditions of Christmas, the delights of the senses that go naturally with the season. Eat, drink, sing, laugh, dance, come in before His presence with exceeding great joy. Why, after all, do we have bodies?

“Man, though made of body and soul, is a unity,” says the Catechism of the Catholic Church. “Through his very bodily condition he sums up in himself the elements of the material world. Through him they are thus brought to their highest perfection and can raise their voice in praise freely given to the Creator. For this reason man may not despise his bodily life. Rather he is obliged to regard his body as good and to hold it in honor since God has created it and will raise it up on the last day.”

This is what Jesus taught us: We have bodies so that we can use them to worship God, as Jesus of Nazareth did. We have bodies so that we can use them to serve others, as Jesus of Nazareth did. We have bodies so that we can bring comfort and consolation and healing, as Jesus of Nazareth did. We have bodies for glory’s sake.

And Christmas is full of that glory. The Gloria, the song of Christmas, comes to us from the Christmas Eve mass of the ancient Church. The angels sang it when they announced Christ’s birth: Glory to God in the highest! What was so glorious? This Jesus was born to a poor working family in a drafty stable filled with smelly animals. And that is precisely what was so glorious. There was nothing idealized about Jesus’ birth. The Son of God was born in an absolutely ordinary way. The first people to hear of the miracle were certain poor shepherds — not the great and mighty Emperor Augustus in his palace at Rome, not even that tin-plated despot Herod. That is the wonder of the Word-made-flesh: the Word was truly made one of us.

The Christmas story is the story of how the flesh became holy, the body was sanctified, and simple earthly joys became hymns of praise to God. Thus Christmas is a feast for the eyes, the ears, and all the senses. We love to hear the story over and over, and we always will love it so long as a scrap of humanity remains in us.